1. Field of the Invention
The present invention relates to a process for production of semiconductor device and a cleaning device used in the method.
2. Description of the Related Art
In the process for production of semiconductor device, each semiconductor wafer after the step of wiring pattern formation thereon is cleaned to remove the foreign matter and residue appearing during said step and adhering to the wiring.
The above step of wiring pattern formation is ordinarily conducted as follows. On the semiconductor substrate on which semiconductor elements have been formed, is formed a metal film made of a wiring material; then, a resist film is formed on the metal film; the resist film is subjected to photolithography to form a fine resist pattern; using the resist pattern as a mask, the metal film is dry-etched; and the resist pattern on the metal film is removed by plasma ashing or the like, to form a wiring pattern. In this step of wiring pattern formation, however, foreign matter and residue appear at the time of dry-etching of metal film and subsequent removal of resist pattern and adhere to the metal wiring. The foreign matter and residue adhering to the metal wiring give rise to various wiring defects, incurring reduction in productivity as well in performance and reliability of final product, i.e. semiconductor device. Therefore, in order to remove the foreign matter and residue, cleaning is conducted after the step of wiring pattern formation.
For cleaning of the foreign matter and residue, there is ordinarily conducted wet cleaning using an organic cleaning solution, an acidic cleaning solution, an alkaline cleaning solution or the like, after which rinsing with pure water is conducted lastly.
When the wiring pattern is fine, cleaning of the foreign matter and residue is conducted by using, as the cleaning solution, mainly an organic cleaning solution which gives relatively low corrosion to the metal wiring. Ordinary organic cleaning solutions, however, are low in cleaning power and have various problems; for example, a treatment using an aqueous alkali solution (has corrosivity) is necessary before the cleaning with organic cleaning solution because of its low cleaning power, and prerinsing using an organic solvent of high flash point (e.g. isopropyl alcohol) is necessary after the cleaning with organic cleaning solution but before rinsing with pure water.
Hence, an organic cleaning solution containing a fluorine compound (e.g. ammonium fluoride) is in use in place of the ordinary organic cleaning solution. This organic cleaning solution comprises a fluorine compound (e.g. ammonium fluoride), a solvent (e.g. dimethyl sulfoxide) and water in given proportions. The ammonium fluoride contained in the cleaning solution has an action of removing the metallic foreign matter and residue adhering to metal wiring (their removal with solvent is impossible), by etching the oxide-film formed spontaneously between the wiring and the foreign matter and residue adhering to the wiring. Meanwhile, the solvent contained in the cleaning solution dissolves and removes resinous foreign matter and residue. Consequently, the organic cleaning solution containing a fluorine compound can sufficiently remove both the metallic foreign matter and residue and the resinous foreign matter and residue, and no treatment using a corrosive alkali solution is necessary. Further, the organic cleaning solution exhibits the above-mentioned excellent cleaning power at relatively low temperatures of about room temperature (25.degree. C.). Furthermore, since the organic cleaning solution has been thought to show substantially no corrosiveness to the metal wiring, no prerinsing has been conducted and rinsing with pure water has been conducted right after the cleaning with the organic cleaning solution. Incidentally, prerinsing incurs an increased cost due to the use of prerinsing solvent, requires an additional step of prerinsing and also a step of disposal of waste solution and, therefore, makes, the whole process disadvantageous; moreover, the fluorine compound and the prerinsing solvent react with each other in some cases, which poses a problem. Thus, it is preferred that no rinsing is conducted.
Other cleaning solutions containing a fluorine compound are disclosed in JP-A-7-271056. In the literature are disclosed a peeling solution for photoresist, consisting of an aqueous solution comprising a particular ammonium salt of organic carboxylic acid or a particular amine salt of organic carboxylic acid and a fluorine compound in given proportions; and a peeling solution for photoresist, consisting of an aqueous solution comprising a particular ammonium salt of organic carboxylic acid or a particular amine salt of organic carboxylic acid, a fluorine compound and a particular organic solvent in given proportions.
In recent years, as semiconductor devices have become smaller in size and more highly integrated, a finer wiring pattern has become necessary, and the width of each wiring and the distances between adjacent wirings have become finer. In cleaning of such a fine wiring pattern, even very slight corrosion of wiring (which has not been a problem in cleaning of conventional wiring pattern) changes the size (dimension) of wiring pattern significantly, and the wiring pattern after cleaning is different from the dimension of designing stage. As a result, the wiring pattern after cleaning comes to have various wiring defects such as poor contact, short-circuiting and the like.
Thus, even in the cleaning with the abovementioned cleaning solution containing a fluorine compound, there has come to arise a problem that a wiring is corroded in the pure water rinsing after cleaning with the above cleaning solution. The corrosion of wiring in the pure water rinsing is particularly striking when a plurality of semiconductor wafers are arrayed at given intervals and they are cleaned and rinsed together. Treating a plurality of semiconductor wafers together is essential for simplification of production process and lower cost. Therefore, striking appearance of corrosion in such treatment is a serious problem because the request for semiconductor device of lower cost is becoming increasingly higher.